If stars we see are billions of years dead, what is really out there now?

Question

They say that when we look up to see stars, we’re actually seeing the light from dead stars. So technically, we can’t see what’s out there in the present? What do you think is out there now? is it just new, modern stars or we don’t get to see anything at all? (since by now, everything has expanded billions of miles apart from each other that light is far from anything to reach)

In: Planetary Science

Answer 1

No they aren’t.

The stars we can see with out naked eyes aren’t that far away.

Most stars we can see are less than a 1000 light years away.

Our entire galaxy is only 100,000 light years across.

The shortest lived stars are very rare blue super giants which last for 10 million years.

Our own sun is 5 billion years old and will last for maybe 9 or 10 more billion years.

Red dwarfs, which are the most common type of star can last for trillions of years.

So in terms of how long stars last the delay of us seeing them of a few years, decades, centuries or even millennia is nothing.

The farthest object we can see with our eyes is the Andromeda Galaxy, we can only see it under ideal conditions like out in the country where the air is clean and there isn’t much light pollution and even then we can’t make out any details, but the distance is large enough that some of the shorter lived stars we see in there are almost certainly dead by “now”.

For object farther away viewed big telescopes and other instruments the certainty is much bigger. Especially since the brightest things tend to be the most short lived (in general if not in ever individual case).

Of course “now” or “at the same time” are not really concepts that hold any really meaning on these scales. Relativity means that such things don’t really work the way we normally think of them.

So yes keeping in mind that “now” is not really a thing, a few of the nearer objects and many of the more distant objects no longer exist “now”.

However we do have a good understanding of how stars live and move and die. We know their lifecycle and can make pretty good guesses how stars and larger objects have changed over time since they emitted the light we see.